1. Technical Field of the Invention
The present invention relates to a musical sound signal generation apparatus for generating musical sound signals of tones of a piano type musical instrument in response to a note-on instruction and a note-off instruction of a musical sound at a desired pitch, a damper-pedal-on instruction, and a damper-pedal-off instruction.
2. Description of the Related to Art
Attempts to electronically reproduce musical sounds generated from a natural musical instrument by simulating the action of the natural musical instrument have been made.
Among natural musical instruments, in a piano, for example, a sound is produced when a hammer strikes a string corresponding to a depressed key of a keyboard among a plurality of arranged strings, and releasing the key triggers a damper to come into contact with the string to suppress vibration of the string, thereby stopping the sound. When a certain string is struck, not only does the string generate a sound but neighboring strings resonate or the vibration of the string is propagated to other strings through a sound board to vibrate the other strings, and thus the other strings also generate sounds. This resonance or propagation of vibration is an important element of the characteristic sound of a piano. Meantime, a sustain pedal is known which separates dampers from all strings and prevents a damper from coming into contact with a string even when a key corresponding to the string is released.
Attempts to electronically reproduce the characteristic sound of a piano are disclosed in several Japanese Patent Publications.
Japanese Patent Publication No. 2828872 describes that a resonant sound generation channel is set for a string corresponding to each pitch, and a musical sound signal of a pitch corresponding to a depressed key, which is generated by a sound source, is input to the corresponding resonant sound generation channel so as to generate a resonant sound corresponding to the pitch. In addition, it is described that a resonant sound is generated only for a string from which a damper is released by controlling a coefficient for determining a level of a musical sound signal input to each resonant sound generation channel in response to a damper state determined according to on an on/off state of each key and an on/off state of the sustain pedal.
Japanese Patent Publication No. 2650509 discloses that a musical sound signal that simulates vibration of a string of a piano is input to a filter that simulates a propagation state of vibration from a bridge to a sound board in the piano, and a musical sound signal output from the filter or a musical sound signal before being filtered and the musical sound signal output from the filter are output as sound of a musical sound.
Japanese Patent Publication No. 2917609 describes that signals representing vibration states of strings corresponding to respective keys of an acoustic piano, a piano frame and a board support are stored in advance and when key depression is detected, signals indicating vibration states of the corresponding string, piano frame and board support are read according to information on the key depression (key number, hammer velocity, etc.) and supplied to a sound board driving section so as to drive a sound board, thereby generating a sound having the same tone as that of the acoustic piano.
In an acoustic piano, vibration is propagated from a certain string to another string via the air, a bridge, a frame, etc. This propagation is not affected by a damper state in each string (whether or not a damper comes into contact with a string).
Accordingly, the method of controlling a level of a musical sound signal input to each resonant sound generation channel according to a damper state, as described in Japanese Patent Publication No. 2828872, cannot correctly reflect the physical structure of the acoustic piano.
In addition, in the acoustic piano, vibration propagated from a certain string to another string is further propagated from another string to still another string. However, the method disclosed in Japanese Patent Publication No. 2828872 cannot reproduce propagation of vibration from another string of a propagation destination to still another string.
Japanese Patent Publication Nos. 2650509 and 2917609 do not describe a musical sound signal generation algorithm which solves the above problem.